The present invention relates to lower member fixing methods useful for fixing to a support member a plurality of lower members each having at least one reference bore for installing an upper member.
The terms "upper member" and "lower member" as used herein refer respectively to a member away from the support member and a member closer to the support member,
For example, fluid control apparatus for use in semiconductor manufacturing equipment are assembled by fixing a plurality of couplings (lower members) to a base plate (support member) and fixing a functional member (upper member) such as an on-off valve or massflow controller, as positioned on these couplings, to the couplings.
For use in assembling the fluid control apparatus, the base plate is formed with threaded bores, the couplings are each formed with insertion holes for inserting therethrough coupling fixing bolts to be screwed into threaded bores of the base plate and with threaded bores for functional member attaching bolts, and the functional member is formed with insertion holes for the functional member attaching bolts. When the couplings are fixed to the base plate by the coupling member fixing bolts, the functional member attaching bolts can be readily screwed into the respective threaded bores of the couplings, with the joints between the functional member and the couplings sealed off.
However, since play is provided inside the bolt insertion hole of the coupling around the coupling fixing bolt, the interval between the threaded bores of adjacent couplings is likely to vary by an amount corresponding to the play. The conventional method therefore has the problem that the bolt insertion holes of the functional member are not always in register with the corresponding threaded bores of the couplings in installing the functional member on the couplings, presenting difficulty in attaching the functional member to the couplings.
Furthermore, the fluid channel of the coupling will not be in alignment with the corresponding fluid channel of the functional member as specified, entailing the problem of impaired sealing.